Casting polyurethane formed by a prepolymer method or a one-shot method is excellent in mechanical properties such as wear resistance and impact resistance, and is used for various industrial applications in the form of industrial products such as rolls and belts.
On the other hand, optical applications such as optical lenses and optical components recently require not only excellent optical characteristics but also outstanding mechanical properties such as impact resistance. Therefore, the use of casting polyurethane for optical applications is considered.
There have been proposed a polyurethane resin composition for casting prepared from a polyisocyanate selected from 4,4′-methylene-bis(cyclohexyl isocyanate) or isophorone diisocyanate, a polyhydroxy compound selected from a polyether diol or a polyester diol having an average molecular weight of 700 to 1200 or their mixture, and an aromatic polyamine made of 4,4′-methylene-bis(2-chloroaniline); and an impact-resistant optical lens formed by casting the polyurethane resin composition for casting (see, for example, the following Patent Document 1).    Patent Document 1: Japanese Unexamined Patent Publication No. 2002-187931